Electrical musical instrument



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Feb. 9, 1943. J. M, HANERT 2,310,429

ELECTRICAL MUSICAL INSTRUMENT Filed Sept. 22, 1941 2 Sheets-Sheet 2 ff? z/ef? for Patented Feb. 9, 1943 UNITED STATES PATENT OFFICE 2,310,429 ELECTRICAL MUSICAL INSTRUMENT John M. Hanert, Wilmette, mond Instrument Com poration of Delaware Application September 22, 1941, Serial No. 411,804

(Cl. S11- 1.25)

20 Claims.

My invention relates generally to electrical musical instruments, and more particularly to musical instruments of the melody type, and constitutes an improvement on the instrument disclosed in the patent to Laurens Hammond and John M. Hanert, No. 2,223,258, issued February 25, 1941.

In playing certain types of music, it is desirable at times to produce a plurality of melody tones which are related by octaves in much the same manner as in the orchestra, where a relatively large number of instruments may all be playing the melody part but are separated by octave intervals. At present, this eiect may be achieved by a relatively large number of players, each playing a melody instrument of the type disclosed in the aforesaid patent to Laurens Hammond and John M. Hanert.

Inasmuch as all of these players are playing the same melody part, it would be desirable to produce this orchestral eiTect by a single player playing upon a single keyboard. This keyboard may or may not be attached to a piano, as illustrated in the aforesaid patent.

Itis accordingly the main object of this invention to provide means whereby, with a single keyboard, the musician may produce a plurality of octave related tones which in themselves emit their sound from spatially separated electroacoustic translating systems, and may also be individually controlled as to dynamic envelope and quality of tone. Thus, the only relation which these sources of sound bear to each other isthat they are of exact bear exact octave relation to each other is of course desirable from a tuning standpoint.

It is thus an object of my invention to provide an improved melody instrument having a keyboard of a range of several octaves by which a plurality of tones may be simultaneously sounded in octave or multioctave relationship but of different tone qualities.

A further object is to provide means for producing octave related tones from a plurality of electroacoustic translating sources to produce an orchestral acoustic perspective.

A further object is to provide means whereby a plurality of octave or multioctave tones may be produced with diiierent dynamic tone envelopes.

A further object is to provide an improved relay keying system in connection with the keylwoard having a plurality of contacts for transmission of octave or multioctave related signals octave relationship. Thefact that the tones have frequencies which do Ill., assigner to Hampany, Chicago, Ill., a corfrom a common generating source to a plurality of tone controlling meshes and electroacoustic translating means.

A further object is to provide a plurality of non-linear transmission systems for the production of a plurality of tones of differing tonal character.

A further object is to provide a unitary volume controlling system for simultaneously varying the acoustic output of a plurality of independent electroacoustic translating systems.

A further object is to provide a plurality of signal transmission systems in which individual switching means are provided for varying the intensity envelope.

A further object is to provide a plurality of electroacoustic translating means with signals of varying tone color and selectively imparting a tremolo or vibrato effect.

Other objects will appear from the following description, reference being had to the -accompanying drawings in which:

Figures 1 and 2 constitute a diagram of the instrument.

General description As shown in Figures 1 and 2, the keyboard of the instrument comprises a plurality of keys, being designated CI to B3, inclusive. The actual pitches of the tones produced upon depression of these keys may be varied as desired by register controlling switches such that the notes produced upon depression of the keys may be selectively in the bass, tenor, contralto or soprano registers. As a result, the keyboard may, by the use of such register controlling switches, be made to sound any note within a six octave range. A plurality of groups of register controlling switches are provided, and it is possible further to provide means for simultaneously sounding a plurality of octave related frequencies by each of these groups of register controls.

In general, the instrument comprises a single master occillator IU which is connected to control a series of six relaxation oscillators I2 to I1, inclusive, which are connected in cascade and have their frequencies of oscillation stabilized by a signal derived from the master oscillator I0. A plurality of tuning condensers CI to CI2 are provided for tuning the master oscillator, and a plurality of tuning resistors RI to RII function to condition the relaxation oscillators to successively divide the master oscillator frequency by a factor ot two, thus providing a complete Wiring -to tune the range oi' the instrument. Resistors Ri2, RI8 and'RI8, together with resistors RI toItII, constitute a voltage dividing -mesh for applylnl appropriate controlling grid bias to the controlled oscillators. The controlled oscillators Il to I1 are illustrated merely as blocks for simplifying the wiring diagram. The complete circuits together with a description oi their operation appears in th'e aforesaid patent to Laurens Hammond and John M. Hanert.

As disclosed in said patent, the frequencies of the master and controlled oscillators shift simultaneously upon depression of one of the playing keys (except the B" keys), which results in connection ofthe corresponding tuning contacts Cia to A#8a to ground via one of the relay tuning contacts 80a, 8Ia or 82a. A second sequentially operated key switch Clb to B311 closes to operate relay solenoids 88, 8| or- 52 via a circuit comprising interlocking relay contacts 8811, 8Ib and 82h, this circuit being completed through voltage dropping resistors RI8 and R28 to conductors 80, through series relay coil 88, through conductor 82 to terminal 88, and thence through resistor R22 to a terminal +300 v. of the power supply system. A resistor R88 connects terminal 88 to ground. Thus, each of the keys in the lowest octave may operate relays 50 and 88, keys in the middle octaves operate relays 48l and 88, and depression of any key in the highest octave will operate relays 82 and 58. Resistors R28, R28, R28, R30 and R32 serve to suppress sparks which might otherwise be produced incidental to closing the circuits associated with relays 80, 8|, 82 and 58, respectively. It is to be noted that every time a playing key is depressed, the voltage at the junction point 88 of the voltage divider resistors R22 and R38 is reduced in value. This is because the resistance of the relay circuit is putin shunt with the resistor R38. As will be explained hereinafter, this change in potential results in the removal of the cutoi bias from control tubes 88, 88, 10 and 12.

In addition to opening switches 50h, 5Ib and 5217 and closing switches 50a, 5Ia and 82a, the relays I and 52 close switches 80e, 5Ic and 52e. These switches are provided to operate in the manner disclosed in my co-pending application Serial No. 361,064, filed October 14, 1940. Resistors R38 and R31, which are connected in series with the lower contacts of the switches 50c, 5Ic and 52e and conductor 88, are provided for the purpose of matching the amplitude of the .signal between the highest note (BI) of the lowest octave group, and the lowest note (C2) of the middle octave group. and also between the highest note (B2) of the middle octave group and the lowest note (C3) of the highest octave group. The relays 50, 5I and 52, upon energization, also open switches 80d, 5|d and 52d respectively.. The upper contacts of 50d, Iiid and 82d are connected to a point of fixed direct current potential indicated as v. providing a signal return terminal for unused signal circuits, thus preventing signal flow through spurious paths in unused register control circuits. The movable contacts of switches 50d, 5Id and 52d are connected to collector buses 68. 88 and 10 reasians to the terminal +10 v. through load resistors R38, R38 and R88 respectively.

Signals from the oscillators I0 and I3 to I1, inclusive, are selectively impressed upon the collector buses 88, 88 and 10 by operation of register control tablets 1i. 12, 13 and 18 for eectively shifting the gamut of the keyboard to the soprano, contralto, tenor and bass" ranges respectively. Each of the register control tablets 1I to 18 is adapted to operate three switches designated by the tablet reference character followed by the letters a, b and c respectively, as lla, 1lb, 1Ic. The lower contacts of the switches 1Ic, 12c, 13e and 18o are connected to the collector bus 88, while similarly, the lower switches of the contacts 1lb, 12b, 13b, 18h are connected to the conductor 89, and the lower contacts of the switches 1Ia, 12a, 13a, 18a are connected to the bus collector 10. The upper contacts of the switches 1Ia to 18a, 1lb to 1lb, and 1Ic to 18e are respectively connected to appropriate output terminals 22, 28, 28, 28, 80 and 32 of the oscillators I8 and I3 to I1, inclusive, through decoupling resistors R82.

By selective operation of the register controls 1I to 18, signals from any three adjacent oscillators, or from any number of groups ofvthree adjacent oscillators, may be conditioned for f connection to the signal output conductor 88 spectively, and each of these buses is connected upon depression of keys in the three octave groups.

The relays 50, 5I and 52, upon energization, also close switches 50e, 5Ie and 52e, and open switches 50], 5I! and 52f respectively. The switches 50e, 8Ie and 52e correspond respectively with the switches 50c, 5Ic and 52c, while the switches 50i, 8If and 82;! correspond respectively to the switches 50d, 5Id and 52d. 'I'he lower contacts of switches 50e, 5Ie and 52e are interconnected by resistors R83 and R88, which function in the same manner as resistors R38 and R31 and are connected to the output conductor 18.

The upper contacts of switches 50e, 5Ie and 52e are connected to collector buses 18, 19 and respectively, these buses also being connected to a constant potential terminal +10 v., through resistors R88, R89 and R50 respectively. The upper contacts 50j, 5If, and 52.1c serve to connect unused collector buses 18, 19, 80 to the +10 v.

terminal, and thus provide a negligible impedance shunt for any possible spurious signal paths. A second set of register control tablets 8i, 82, 83 and 88 are each adapted to close three switches to complete signal circuits (similar to those previously described with reference to register controls 1.I to 18) to the bus collector 18, 19 and 80. Suitable generator decoupling resistors R82 are provided in each of the tablet operated switch completed circuits.

From the foregoing it will appear that upon depression of a key, for example the key CI ln the lowest octave, the master oscillator I0 will be tuned to the C frequency (2093 c. p. s.), and as a result, all of the controlled oscillators I3 to I1 will be caused to oscillate at successively lower octave interval frequencies. The depression of the key CI will also cause energization of the relays 52 and 58 through a circuit including the winding of the relay 52 (shunted by resistor R28), relay switch 5Ib, resistances RI8 and R20, conductor 60, winding of relay 58 (shunted by resistor R32), and conductor 82 to terminal 88. Terminal 68 is normally at a potential of approximately H65 volts due to the voltage dividing effect of the resistors R22 and R84. Upon operation of the relays, the circuit .lust described is eectlvely in parallel with the resistor R84, so that the potential at the terminal 84 will drop kconsiderably to a value such as +50 volts.

Energization of the relay 82 will cause the following to occur:

(1) By opening the switch 82h, energization of the relay 8| is precluded from operating should an additional key be depressed inthe middle octave while holding down the aforesaid key Cl in the lower octave.

(2) Closure of the switch 82a results in completion of the tuning circuit between tuning contact C la and ground.

(3) Assuming that the register control 1| has been operated to close switches -Ila, '1lb and Hc, closure of the switch 82o will, by connecting the bus collector 18 to the conductor 88, complete a signal circuit from the output terminal 28 of the third controlled oscillator to the conductor 88.

(4) Opening contact 82d will disconnect the bus collector 18 from the terminal +10 v., which latter is effective as a signal return for unwanted signals.

(5) Assuming that the register control 84 has been operated to close its associated switches, closure of the switch 82e will result in connecting the terminal 32 of the sixth controlled oscillator through its decoupling resistor R42 to the bus collector 88, and the latter to the signal conductor 18.

(6) Opening of the switch 821 results in disconnecting the bus collector 88 from the +10 v. terminal which, prior to the opening of the switch, served as a return for the previously unused signal from terminal l2.

From the foregoing, it will be seen that the conductor 18 will thus have a signal of the lowest C (65.406 c. p. s.) impressed thereon from the sixth controlled oscillator I1, while the conductor 88 will have a signal of C (523.25 c. p. s.) from the second controlled oscillator I3 impressed thereon. While the oscillators are described as generating certain predetermined frequencies, it will be understood that the output signals therefrom are rich in harmonics, as more fully described in my co-pending application Serial No. 284,325, filed May 18, 1939.

The conductor 88 is connected to a preampliiler 88, while the conductor 18 is connected to a similar preamplifier 88. The outputs of the preampliflers 88 and 88 are selectively fed through mute tubes 88 and 8| respectively, or shunted around these tubes upon closure 0f switches 82 and 83 respectively. The quality of the tones may be controlled by utilizing various sections of filtering meshes 84, 95, which are connected in the signal circuits. While the meshes 84 and 95 are illustrated as being identical, the values of the elements thereof preferably are made different so that the resonance peaks of one mesh occur at frequencies differing materially from the frequencies of the resonance peaks of the other mesh.

The mute tubes 88 and 8| operate non-linearly ,to change the quality of the tone signal fed there through in a manner more fully disclosed and claimed in my co-pending application Serial No. 361,064, filed Octoberlfi, 1940. These tubes serve to reduce the harmonic content of the signal in a non-linear manner. The signal, as modified by the tone controlling mesh 84 and by the mute tube (if the latter is connected in the circuit), is supplied to the primary winding of a coupling transformer Ti. Similarly, the signal from the conductor 'I8 as modified by the nltering mesh 8l and by the mute tube 8| (if the latter is connected in the circuit), is supplied to the coupling transformer T2.

The secondaries of the transformer Ti and T2 are respectively coupled in push-pull arrangement with remote cutoff pentodes 88, 88 and 81, 88. These tubes serve selectively to control the intensity envelopes of the ultimate sound signal produced, insofar as percussion effects are concerned, and for this reason, will hereinafter be referred to as percussion tubes and are so designated in the drawings. These percussion tubes 88 to 88 inclusive preferably are of the remote cutoff type such as the K'lG type.

The cathodes, such as 88k, are shownconnected to ground, and the suppressorgrids, such as 88c8, are shown connected to the cathodes. The screen grids, such as 8802, are maintained at a fixed potential of v. The plates of these tubes, such as 88p, are connected to a point of fixed potential of +300 v. through plate load resistors R48.

When the elements are thus connected, the tubes will function when a signal of suitable amplitude is impressed upon their grids. to produce output signals which may be varied in intensity by adjustment ofthe control grid bias. Such adJustment is shown as provided in the following manner. The center tap |88 of the secondary or transformer T2 is connected through a resistor R48 to a switch |82, which may be connected either to a terminal -25 v. or -50 v., depending upon the decay characteristics of the tone intensity envelope desired. When the switch |82 is connected to the terminal 25 v., the decay will be less rapid and will ilnally attain a medium level as represented by a negative 25 volt bias, and the signal will be maintained at this level as long as the key is held down. On the other hand, if the switch |82 is connected to the -50 v. terminal, percussive tones will decay relatively rapidly to substantially zero intensity, since the negative 50 volt bias on the control grids represents substantial cutoff for the type of tube used.

When the percussion effect is not desired, a switch |84 is closed, thus connecting the center tap |88 of the transformer T2 through an attack resistor R88 and an anti-spark resistor RBI to a terminal 10 v. of the power supply system. Under these circumstances, the resistors R58 and RBI, together, are of low value with respect to that of resistor R48, so that when the switch |84 is closed, the potential on the grids will be maintained at a value approaching -10 volts. Thus, under these conditions, the percussion tubes 81 and 88 operate merely as repeaters and do not ail'ect the intensity envelopes of the transmitted tone signals.

It will be recalled that when any of the playing keys is depressed, the relay 84 is energized, This relay, among other functions, controls the operation of a single-pole, double-throw switch, the movable switch arm |88 of which is connected to ground through an envelope controlling condenser CI8. The switch arm |88 normally engages a contact |88, which is connected through the anti-spark resistor RSI to a constant direct current potential source indicated as -10 v., thus normally maintaining a charge of -10 volts across the condenser Cl8.

Upon energization of the relay 84, the movable switch arm |88 disengages contact |88 and en gages contact |I0, and thereby connects the ungrounded terminal of the condenser CIS to the center tap of the secondary of transformer T2 through the attack resistor R50. The rate at which the charge from the condenser CIS is effective to change the potential on the center tap |00 is determined by the relative values of the condenser C|6 and resistor R50, as well as by a condenser CI8, which latter condenser is connected between the tap |00 and ground. It will be understood that since the grids of the percussion tubes draw negligible current, the determination of the grid bias may be accomplished by small condensers and high value resistors, because the voltages present, rather than the current ow, are of primary importance in determining the gain of the percussion tubes.

The relay 54 also operates a switch arm |0611 which is normally in engagement with contact |0811. Upon energization of the relay, the switch arm |06a breaks contact with |0811 and completes a circuit with a contact H011. The contact |0811 is connected through an anti-spark resistor R5|a to the terminal i-lO v., while the contact |I0a is connected to the center tap |0001 of the transformer TI, through an attack resistor R50a.

The contacts I 08a and |I0a are adapted to be connected together by a manually operable switch |0411. It will be apparent that the switch |0611 and its associated circuits are similar to switch |06 and its associated circuits respectively and control the percussion tubes 96 and 98 in the same manner that the switch I 06 and its associated switch circuits control the percussion tubes 91 and 99 as above described. The secondaries of transformers T3 and T4 are respectively connected to the grids of tubes 10, I2 and 66, 68 which serve as control tubes determining the over-all volume of the outputs of the two systems, and for affecting the character of the attack and terminal decay portions of the intensity envelopes of the transmitted tones.

By virtue of the fact the tubes 96 and 98, as well as the tubes 91 and 99, are connected in push-pull, any transients in their plate circuits incident to the initiation and cessation of plate current, will be substantially cancelled. Also, the push-pull arrangement results in the cancellation of undesirable even order harmonic distortion terms.

The gain of the control tubes 10, 12 and 66, 68 are controlled by varying their grid bias, and for this reason, these tubes are preferably of the remote cutoff type such as the BKIG. 'I'he volume or gain control may be of any suitable construction such as shown in Fig. 2, and comprising a mesh II4. This mesh includes a plurality of resistors R60 which may be of graded values and are adapted to be connected i`n parallel successively upon actuation of a manually or pedally controlled groundedv contactor ||5. The maximum volume, which occurs when all of the resistors R60 are out of the circuit, is controlled by an adjustable resistor RSI, the resistoriRBI being connected between ground and resistor R63. A resistor R63 provides a lower volume limiting means for the mesh II4, and is connected between a terminal ||8 and the ungrounded terminal of the adjustable resistor RBI. It will be noted that one terminal of each of the resistors R60 is likewise connected to the terminal IIB. The terminal ||8 is connected through a decoupling resistor R64 to the center tap |20 of the secondary of transformer T4, and

. tion.

similarly, is connected through a decoupling resistor R6411 to the center tap |2011 of the secondary of transformer T3.

A condenser C20 is connected between the center tap |20 and ground, and a similar condenser C2011 is connected between the center tap |2011 and ground. The condensers C20 and C2011 serve as a means for preventing abrupt changes in voltages at the center taps |20 and |2011 respectively, upon operation of the volume control contactor II5, so that variations in volume of the output will be correspondingly gradual.

It is to be noted that the volume control mesh I4 functions merely to determine the voltage at the taps |20 and |20a, and that there is no appreciable current flow from the terminal ||8 to these center taps. Thus, the Volume control mesh I I4 may be utilized to control any number of output channels similar to the two channels shown.

When it is desired to impart a slow attack to simulate the intensity envelope of a bowed string tone, the switch |22, or the corresponding switch |2211, is closed to connect the center tap |20 (or |2011) to the cathodes of tubes 66, 68 (or 10, 12), through a condenser C22 (or C2211). The condensers C22 and C22a affect the rate at which the cathode-grid bias on tubes 66, 68, 10, 'I2 changes upon changes in potential at the terminal 64 due to completion of a circuit through one of the` relays 50, 5| or 52 and 5,4. In a somewhat similar manner, a large condenser C24 serves to render the decay envelope gradual upon release of any key. A detailed description of the manner in which the condensers C22 and C24 operate to control the characteristics of the intensity envelopes is disclosed in the aforesaid Patent No. 2,233,258.

The outputs of the tubes 66, 68 and 10, 'I2 are resistance-capacity coupled to suitable power ampliers |26 and |2611, the power amplifiers being transformer-coupled to the voice coils of speakers |28 and |2811. In order to provide for variation in the outputs of the two channels, it is desirable to provide adjustable resistors R10 and RIa in the voice coil circuits of the speakers |28, |28a. In this way, the relative volumes of the two systems may be varied, and such variation will be substantially uniform throughout different settings of the volume control mesh I I4.

The speakers |28 and |28@ are preferably equipped with acoustic frequency modulators |30, |30a which may be of any suitable constructype disclosed in the co--pending application of A. W. Wells, Serial No. 404,099, led July 26, 1941, which comprise a rotating sound deflecting surface operating lto modulate` frequencies at a vibrato rate due in part to the Doppler effect. The acoustic frequency modulators |30 and |3011 are preferably each provided with individual controls |32 and |3211 so that they may be selectively utilized by the player.

In operation, the musician depresses the keys CI to B3 in the usual manner of a melody instrument, but instead of producing but a single tone, by suitably adjusting the various controls and switches, the musician has available the possibility of producing a large variety of tonal effects, not only as to a single melody tone but as to an accompaniment tone which may have characteristics of tone quality and tone envelope differing greatly from that of the melody tone. For example, if it is desired to play a musical selection in which the leading melody part pref- These modulators may be of the general y erably consists of a-rich full organ background, together with a percussive bell-like tone for accentuating the notes, the controls may be set as follows:

In order to produce the full organ effect, the register controls 12, 13 and 14 will be operated to close their respective switches. The switch 92 will be closed and the tone controlling mesh 94 adjusted for approximately uniform frequency response. The switch |04a will. be closed so as to remove the percussion effect. The switch |22a will be closed so as to impart a slow organ-like attack to the tone. The control |32a will be operated to produce a frequency modulating vibrato effect in the output of the speaker |28a.

For the production of the bell-like percusslve tone, the register control 8| will be operated to close .its associated switches. Mute switch 93 will be opened to remove undesirable high order overtones, and the tone controlling mesh 95 will be appropriately adjusted to emphasize the low and high frequencies with a frequency response diminution for middle range frequencies. Switch |02 will be moved to contact the terminal -50 v., and switch |04 will be opened, thus producing a decided percussion effect whenever a key is depressed. Switch |22 is left open so that the tonal attack will be rapid, the control |32 for the frequency modulating vibrato will be turned to its Off position, and volume control resistance R10 will be suitably adjusted to match the volume of the bell tone with respect to the volume of the organ tone.

Since the speakers are spatially separated, the over-al1 musical effect will be that of two separate instruments playing simultaneously, one instrument simulating the organ and the other,

' the two speakunder the conditions set forth.

To summarize, the'following variations may be selectively employed to vary the tonal output of the two speaker channels:

1) The pitch may be adjusted at will, in four octaves, by operation of the register controls 1| to 14 and 8| to 84. Also, these controls may be operated separately, or in combination to produce selective octave coupler effects.

(2) By selective operation of the switches 92 and 93, the harmonic development of the tones may be altered to a pronounced extent, the tonal differences corresponding generally to the differences between the sounds of two instruments of different orchestral tone families, such, for example, as the differences between reed and string tones.

(3) By adjustment of the tone control meshes 94, 95, the player may selectively determine the resonances' and the general brightness or mellowness of the tones.

(4) By adjustment of the switches |22, |22a, |02 and I02a together with |04 and |04a, the player may selectively determine whether the tone shall be of decided percussion, of moderate percussion, or of slow attack organ-like intensity envelopes. A slow-attack slow-decay .intensity envelope may also be produced by closing switch |22, opening switch |04 and setting switch arm |02 to the -50 v. terminal.

(5) By selective adjustment of the adjustable resistors R and R102, the relative volumes of the outputs of the two channels may be controlled.

(6) By selective operation of the controls |32, |32a, the musician may selectively impart a vibrato effect to the outputs of either or both channels.

The keyboard ofthe instrument may be attached to a piano in the manner disclosed in said Patent No. 2,233,258, may be controlled electrically from the keyboard of a pipe organ or similar instrument, or may be set up for operation as a separate orchestral instrument. By increasing the number of output channels to three or more, the output of the instrument may be made more complex, enabling the musician to obtain an added variety of interesting and beautiful musical effects.

In order to add channels, it is necessary merely to provide additional sets of contacts for the relays 50, 52 and 54, and to provide additional sets of register conrols such as the controls 1| to 14 and 8| to 84. In addition, the relay 54 would be provided with an additional switch and associated network similar to the switches |06 and |06a and their associated circuits. The volume control mechanism apparatus ||4 could be common to all of the output channels, or, if desired, two similar volume control devices could be utilized, each controlling the output of one or more of the channels.

For the best musical results, it is usually desirable to provide a separate speaker for each channel, and to separate the speakers in space so as to provide the acoustical perspective associated with orchestral music. However, it may be desirable, for the purpose of reducing the cost of the instrument and possibly for other reasons, to mix the outputs of the control tubes of the various channels, and supply to a common power amplier an electroacoustic translating system.

two channels are employed. In any event, whenever outputs of several channels are mixed, some means will be provided to obtain the adjustment by the variable resistors R10 and R10a, to enable the musician to vary the relative amplitudes of the signals supplied by the several channels connected to the common power amplifier and electroacoustic translating system. When but two channels are employed with a common power amplifier and speaker system, the generating system preferably is provided with vibrato means in a manner similar to that shown in the aforesaid Patent No. 2,233,258.

When the instrument has one of its channels adjusted for percussion tones while the other by playing legato, cause all except the first key depressed to cause production only of the sustained tone, but may, at any time a musical accent is desired, release all of the keys for an instant. In this case, upon the subsequent depression of a key, both the percussive tone channel and thesustained tone channel Will be effective to transmit their tone signals, producing a very desirable musical accent.

run of notes which extends from one of the octave groups of keys into another octave group of keys, a percussive note will sound upon the depression of the first key depressed in each octave group of notes because of the arrangement of the circuits for the relays 50, 52 and 54. However, for short runs Within the range of one octave group of keys, ythe above described percussive or nonpercussive control of the tones by the manner of key depression may be attained.

When it is desired to produce successive percussive tones, it is necessary merely to depress the keys in a detached or non-legato manner.

From the foregoing description, it will be apparent that the invention is not limited to the use of the particular frequency generating means diagrammatically illustrated, but that the broader principles of the invention may be' applied in an instrument utilizing a single Oscillator generator such' as shown, for example, in my copending application Serial No. 361,065, filed October 14, 1940, wherein the signal output of a single generator has its intensity envelope controlled by the signal itself rather than by the keys.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous variations and modifications thereof may be made Without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include Within the scope of my invention, all such variations and modificationswhereby substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. In an electrical musical instrument, a variable frequency generating apparatus, av keyboardv having a, plurality of keys, means controlled by said keys for varying the frequency of operation of said generating apparatus, a plurality of separate output channels for the signals produced by said generating apparatus, separate intensity envelope determining means associated with each of said channels, means controlled by said keys for initiating the operation of said envelope determining means, a signal amplitude controlling means in each of said channels, means under the control of said lkeys for causing operation of said amplitude controlling means, and a volume control circuit common to all of said channels and operable to affect the amplitude controlling means thereof.

2. In an electrical musical instrument, the combination of a variable frequency oscillator, keyboard means for controlling the frequency of said oscillator, a plurality of output channels capable of connection to said oscillator to receive signals therefrom, means in each of said output channels selectively to control the intensity envelope of the transmitted signals, and means to translate into sound the signals transmitted by said channels.

3. The combination set forth in lclaim 2 in which said intensity envelope controlling means of all of said channels have their operation initiated by circuits under the control of said keys.

4. In an electrical musical instrument, the

In playing a long combination of a set of electrical impulse generators operating at octave interval frequencies, playing keys, means controlled thereby for varying the frequencies of operation of said generators, a plurality of output channels, selective means capable of being rendered effective upon I the depression ofa single one of said playing keys for collecting impulses from a plurality of said generators intoeach of said output channels, and means in at least one of said Achannels for selectively altering the harmonic content of the impulses transmitted thereby. Y

5. The combination set forth in claim 4 in which each of said output channels includes a tone intensity envelope controlling means, and means energized by operation of said keys for controlling the operation of all of said intensity envelope controlling means.

6. In an electrical musical instrument, the combination of an electrical impulse generator, key controlled means for varying the frequency of operation of said generator, la plurality of output channels including electroacoustic translating means, selective means for transmitting impulses -from said generator into said output channels, and means in at least one of said channels for selectively introducing a vibrato effect in the tones produced by its electroacoustic translating means.

'7. In an electrical musical instrument, the combination of an electrical impulse generator, key controlled means for varying the frequency of operation of said generator, a plurality-of output channels, selective, means for transmitting impulses from said generator into one or more of said output channels, and means in at least one of said channels for selectively altering the harlIononic content of the impulses transmitted there- 8. In an electrical musical instrument, a variable frequency generator.V of electrical musical tone signals, a key for controlling the frequency of operation of said generator, a plurality of output channels for receiving signals from said generator, each of said output channels including an electroacoustic translating means, and selectively operable means associated with each of said electroacoustic translating means to in; tioduce an acoustic vibrato in the output thereo 9. In an electrical musical instrument, the combination of a variable frequency generator, a plurality of separate signal transmission control means, selectively operable switches to connect said control means to said generator, a terminal on each of said control means Whose D. C. potential has an effect upon the acoustic envelope of the signal transmitted by said control means, means connecting all of said terminals together, a keyboard, and circuits completed by operation of its keys for determining the frequency of said generator and for connectp ing said terminals to a source of D. C. potential for changing the potential of said terminals, thereby to cause said plurality of control means to transmit signals of desired frequency from said generator.

10. An electrical musical tone signal generating system, including a plurality of variable frequency generators interlocked to operate at octave interval frequencies and having a plurality of separate output channels, keys for controlling the transmission of signals from said generating system to said output channels and for determining the frequency of operation of said generators, means associated with each of said channels for determining the rate of attack of the tone signals transmitted thereby, and a circuit completed umn operation of any one of said keys to initiate the operation of said rate of attack determining means.

11. In an electrical musical instrument, variable frequency signal generating means, a plurality of output channels for transmitting the signal produced by said means, a separate circuit associated with each of said channels for determining the rate of amplitude increase of the signals transmitted through said channels, a keyboard having a plurality of keys, means controlled by said keys for initiating the operation of said amplitude increasing circuits, an output volume control circuit associated with each of said channels, and electrical means common to all of said channels for controlling said volume control circuits.

12. In an electrical musical instrument, the combination of interlocked variable frequency generators of musical signals operating at octave interval frequencies, a plurality of output channels for receiving signals from said generators, key operated means determining the frequency of operation of said generators and for controlling the transmission of signals from said generators to said channels, a terminal in each of said channels, the direct current potential of the terminal determining the amplitude of the sgnal output of the channel, and variable direct current potential means connected to said terminals in all of said channels, thereby simultaneously to vary the amplitude of the signals transmitted by said channels.

i3. In an electrical musical instrument having a multi-octave keyboard and a signal generating system tunable to any one of the semitone frequencies and its octaves, a cut-out relay for each octave of the keyboard, circuits controlled by said relays to render ineiective the remaining relays upon operation of one of them, a plurality of output circuits for signals produced by said generating system, each output circuit having tone intensity envelope determining elements, and a relay connected to be operated upon operation of any one of said cut-out relays and effective to control said envelope determining elements.

14. In an electrical musical instrument having a plurality of playing keys, a variable frequency signal generating system having its frequency of operation controlled by said keys, a plurality of signal transmission circuits, means forming a part of each of said circuits for determining the intensity envelopes of tone signals transmitted thereby, and circuits under the control of said keys for causing said generating system to supply tone signals to said transmitting systems and to control said envelope intensity determining means.

15. In an electrical musical instrument of the melody type, the combination of a keyboard compxising a plurality of keys, a variable frequency signal generating means having its frequency of operation controlled by said keys. a on system for receiving signals from said generating means and having two terminals the potentials of which determine the amplitude of the output signal thereof, switches operable by said keys completing a circuit determining the potential of one of said terminals, and relay means energized by current flow through said circuit for determining the potential of the other of said terminals.

16. The combination set forth in claim in which said relay means includes a resistance and a capacity for controlling the rate of change of the potential on its associated terminal.

17. In an electrical musical instrument, the combination of a variable frequency oscillator, a system of octave interval oscillators controlled thereby, a plurality of separately adjustable output channels, register control devices for selectively connecting one or more of said oscillators to either or both of said output channels, a plurality of playing keys, means controlled by said keys for determining the frequencies of oscillation of said oscillators, means controlling the signal amplitude transmission characteristics of said output channels, and a circuit completed upon operation of any one of said keys to initiate the operation of said last-named means.

18. In an electrical musical instrument, the combination of variable frequency means for generating musical signals, a plurality of output channels for receiving signals from said generating means, a playing key, means operated by said key determining the frequency of said generating means and controlling the transmission of signals therefrom to said channels, a non-linear distorting means in each of said output channels, switches for selectively rendering said distorting means operative, and means controlled by said keys for controlling the amplitude of the signals transmitted by said output channels.

19. In an electrical musical instrument, a variable frequency generator of electrical musical signals, a key for controlling the frequency of operation of said generator, a plurality of output channels for receiving signals from said generator, an adjustable intensity envelope determining means in each of the output channels, and means controlled by said key to initiate operation of said last-named means.

20. In an electrical musical instrument, the combination of a plurality of variable frequency generators of harmonically related frequencies, a plurality of playing keys, means controlled by said keys for determining the frequency of operation of all of said generators, a plurality of separate signal transmission channels, register controls for selecting any or all of said generators for connection to any or all of said channels, and a fixed potential control device in at least one of said channels for altering the intensity envelopes of the tone signals transmitted thereby, whereby the intensity envelopes of tone signals transmitted through said channels may differ from one another.

JOHN M. HANERT. 

